Dual-Comb Spectroscopy For Low-Light Precision Measurements

Ultraviolet spectroscopy is critical for researching electronic transitions in atoms and rovibronic transitions in molecules, which are required for testing fundamental physics, quantum-electrodynamics theory, and precision measurements. Researchers have successfully implemented high-resolution linear-absorption dual-comb spectroscopy in the ultraviolet spectral range, enabling new experiments under low-light conditions and paving the way for novel applications in various scientific and technological fields.

Dual-comb spectroscopy, a potent approach for accurate spectroscopy over large spectral bandwidths, has mostly been employed for infrared linear absorption of tiny molecules in the gas phase. However, it often necessitates powerful laser beams, making it unsuitable for situations where low light levels are crucial. The team has experimentally proved that dual-comb spectroscopy may be used efficiently in low-light circumstances at power levels more than a million times lower than those commonly used.

The researchers solved the hurdles of producing UV frequency combs and developing dual-comb interferometers with lengthy coherence periods, clearing the door for progress toward this desirable goal. They expertly controlled the mutual coherence of two comb lasers with one femtowatt per comb line, displaying an optimal accumulation of the counting statistics of their interference signal across periods greater than one hour.

An attractive potential application is the development of dual-comb spectroscopy at short wavelengths, allowing for precision vacuum and extreme-ultraviolet molecular spectroscopy over vast spectrum spans. Broadband extreme-UV spectroscopy needs better resolution and accuracy and requires specific instrumentation at specialized facilities.

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